At track level, in 14 years I've made 2 Emergency Calls, one to the Signaller and one to the Electrical Control Room.
The one to the signaller was to bring trains to a stop at Gartsherrie because Strathclyde's finest were on the railway wrestling a local ruffian and trains were still running, so they clearly didn't have permission to be there and one came close to getting swiped by a 318 doing 60. The thing about cops is they dress in black, and the thing about night is it's dark, so I doubt the driver of the train even seen him run across in front of the train. Signaller had to bring two freight trains to a stand, and the BTP turned up fairly sharpish to express some words of advice to the civvies.
The one to ECO was done while my colleague was informing the signaller that water was cascading through a tunnel roof and dislodging material (We were doing signal maintenance in a possession, so it didn't warrant the emergency to the signaller as there was no risk to trains), but that the risk of an electrical flashover (arc) from the OLE was incredibly high, which posed a risk to the public. That call bought me and my team a slap up dinner at a Scotrail awards ceremony in Glasgow, as it was deemed that we stopped the tunnel roof from collapsing as a burst water pipe had fairly comprehensivel washed away all the material behind the tunnel wall. Must have cost Scottish Water a fortune as the Kirkhill line had to be shut for a day.